Area Forecast Discussion
Issued by NWS St. Louis, MO

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FXUS63 KLSX 230325
AFDLSX

Area Forecast Discussion...Updated
National Weather Service Saint Louis MO
1025 PM CDT MON AUG 22 2016

.UPDATE...
Issued at 1014 PM CDT Mon Aug 22 2016

Just some high level cloudiness is expected for the rest of
tonight with a surface ridge extending from the OH Valley region
southwest into southeastern MO. Lows tonight will be slightly
warmer than the previous night due to weak southeasterly surface
winds and weak low-mid level warm air advection. Lows tonight will
be slightly below normal for late August.

GKS

&&

.SHORT TERM...  (Through Late Tonight)
Issued at 323 PM CDT Mon Aug 22 2016

SFC ridge will move E thru the OH Vly tonight keeping the FA in
southerly return flow. Models depict bands of low level moisture
convergence that move NE across the area tonight but the column will
not had enough time to sufficiently saturate...so don`t think there
will be much precip prior to 12Z. As such...clouds will be slow to
slow increase from the SW after 6Z. Due to the southerly flow...and
late night clouds...tonight will not be as cool as last night with
most locations in the lower 60s. The exception is locations E/SE/S
of the STL metro where influence of the SFC ridge will be greater
allowing winds to be lighter and clouds will be later to arrive
which will let temps drop a bit more...into the upper 50s. There
could be another round of river valley fog in these same
locations.

2%

.LONG TERM...  (Tuesday through Next Monday)
Issued at 323 PM CDT Mon Aug 22 2016

(Tuesday)

Vort max will quickly eject out of the Red River Valley on Tuesday
morning. This feature combined with broad low-level warm/moist
advection should help maintain what is expected to be isolated-
scattered showers and thunderstorms during the day on Tuesday. Do
not have the greatest confidence in how this activity will evolve
as best moisture convergence during the day on Tuesday outruns the
better DCPVA just downstream of the shortwave trough at mid/upper
levels. Believe some activity will make it into central Missouri
in the late morning timeframe...but uncertain as to exactly how
prevalent the coverage will be...best bet looks like isolated-
scattered. By late afternoon...some of the showers and
thunderstorms may push as far east as the Mississippi River. Highs
on Tuesday will be near that of today...mainly because the low-
level warm advection gets offset by the accompanied increase in
sky cover.

(Tuesday Night - Next Monday)

The remainder of the forecast period continues to look fairly active
with multiple rounds of showers and thunderstorms possible into
early next week. This will be due to a frontal boundary at the
surface which will waver across the mid-Mississippi Valley. Front
will first pass through the CWA on Thursday as a cold front
before moving back to the north and east as a warm front sometime
early next weekend. Certainly will be some dry time across the
area over this period...but presence of frontal boundary beneath
southwesterly flow aloft is suggestive of an overall wet forecast
period. Currently...highest chances of showers and thunderstorms
look to be from Tuesday night through Wednesday night across
northern sections of the forecast area. Highest chances of dry
weather meanwhile would be in what looks to be that short window
between when the cold front progresses through the CWA (Friday)
and the return of the boundary as a warm front into the western
CWA on Saturday.

Temperatures throughout the extended look to be seasonable during
the day and slightly above normal most nights. However...daytime
temperatures will be highly sensitive to degree of cloudiness and
coverage of showers and storms.

Gosselin

&&

.AVIATION...  (For the 00z TAFs through 00z Tuesday Evening)
Issued at 528 PM CDT Mon Aug 22 2016

A large surface ridge centered over the OH Valley region will
continue moving eastward. A light southeasterly surface wind can
be expected tonight on the western periphery of this ridge with a
southerly wind on Tuesday. With increasing low level moisture
along with an approaching weak upper level disturbance there will
be more diurnal cumulus clouds late Tuesday morning and afternoon,
along with the potential for at least isolated shra/tsra. For now
will just include VCTS in the COU taf Tuesday afternoon. It
appears that most of the convection should remain west of the
Mississippi River on Tuesday.

SPECIFICS FOR KSTL: A large surface ridge centered over the
OH Valley region will continue moving eastward. A light
southeasterly surface wind can be expected tonight on the western
periphery of this ridge with a southerly wind on Tuesday. With
increasing low level moisture along with an approaching weak upper
level disturbance there will be more diurnal cumulus clouds late
Tuesday morning and afternoon, along with the potential for isolated
shra/tsra Tuesday afternoon and evening. It appears that most of
the convection should remain west of STL on Tuesday, and
northwest of STL Tuesday evening.

GKS

&&

.LSX WATCHES/WARNINGS/ADVISORIES...
MO...None.
IL...None.
&&

$$

WFO LSX


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